| New Zealand White rabbits with rapid growth and tender meat have become one of the main breeds of meat rabbits raised in China.Rabbit breeding has gradually moved towards intensive farming,and the heavy application of antibiotics can cause drug residues in livestock products and the environment.Many countries have put forward requirements to ban the use of antibiotics,and the search for antibiotic substitution has become a main problem.Intestinal health is a key determinant of disease resistance in rabbits,and the intestinal microbiome,as the "second genome" of the body,is essential for the regulation of cecum microecology in rabbits.Short-chain fatty acids(SCFAs),as metabolic by-products of microbial fermentation of complex polysaccharides,play an important role in regulating animal performance,meat quality and intestinal health with their acetic and butyric acids.In this study,the effects of sodium acetate and sodium butyrate on productive performance,muscle quality,cecum microecology and the mechanism of action of regulating the cell cycle of cecum epithelial cells in rabbits were investigated by constructing rabbit models of sodium acetate and sodium butyrate treatment both in vivo and in vitro,using techniques such as feeding experiments,meat quality determination,multi-omics,molecular biology experiment,cell biology experiment and bioinformatics analysis.The results obtained in this study are as follows:(1)Effect of supplementation of sodium acetate and sodium butyrate to diets on growth performance and metabolism in New Zealand white rabbits.Compared to the control group,FCR and diarrhoea index were significantly reduced in both treatment groups(P < 0.05).Body weight was significantly lower in Acetate group from the 4th to the 6th week and significantly higher in Butyrate group from the 6th to the 10 th week(P < 0.05).ADG in Acetate group was significantly lower in weeks 1 to 7 and significantly higher in weeks 9 to 10,and in Butyrate group,ADG was significantly higher in weeks 2 to 7(P < 0.05).Slaughter indicators showed that the weight of the heart,liver,spleen and lungs was significantly lower in Acetate group,while the weight of the stomach and the length of the small intestine and cecum were significantly higher(P < 0.05);the weight of the heart,liver and lungs was significantly lower and the length of the cecum was significantly higher in Butyrate group(P < 0.05).The serum biochemical and immune parameters showed that the serum levels of GLU,TBA and TC were significantly increased and the levels of ALB,TP,AMY,LPS,t CO2,IL-1β,Ig G and Ig M were significantly decreased in Acetate group(P < 0.05);the serum levels of GGT,TBA,TC,TG,Crea,UREA and GLU,IL-6 and IL-17 were significantly increased and the level of t CO2,IL-1β,TNF-α,Ig G and Ig M was decreased in Butyrate group(P < 0.05),while the two remaining serum biochemical indexes did not change significantly in the two treatment groups(P > 0.05).(2)Effect of supplementation of sodium acetate and sodium butyrate to diets on meat quality of New Zealand white rabbits.The total number and total area of muscle fibers and the amount of crude ash and saturated fatty acids were significantly increased in the quadriceps muscle of Acetate group,while muscle fiber diameter,Phe,Tyr,DAA,and PUFAs were significantly decreased(P < 0.05).The total number of muscle fibers,total area,density and crude ash content were significantly higher and the muscle fiber diameter,Tyr,DAA amount were significantly lower in the quadriceps muscle of Butyrate group(P < 0.05).The types of MUFAs and PUFAs were increased in both treatment groups.(3)Effect of sodium acetate and sodium butyrate supplementation to diets on cecum microecology in New Zealand white rabbitsCecal epithelial length was significantly improved(P < 0.05)and the integrity of the cecum villi was improved in Acetate group.The cecum epithelial length and the number of cupped cells were significantly higher in Butyrate group(P < 0.05),and the cecum villi tissue integrity was improved.The activity or amount of TP,GSH-Px,TSOD,s Ig A,and IL-22 was significantly increased in both treatment groups(P < 0.05).In Acetate group,there was a tendency to increase Na+-K+ ATPase(P = 0.0632),Ca2+-Mg2+ ATPase(P = 0.0986),decrease in flagellin content(P = 0.0980),significant decrease in AMY activity(P < 0.05),and significant increase in T-AOC(P < 0.05).In Butyrate group,the activity or content of Na+-K+ ATPase,Ca2+-Mg2+ ATPase,and TG was significantly higher(P < 0.05),and there was a tendency for flagellin content to decrease(P = 0.1000)and T-AOC(P = 0.0532)to increase.The results of targeted metabolomics of SCFAs from cecum contents showed that sodium acetate treatment significantly increased the content of acetic acid and significantly decreased the content of butyric acid and propionic acid,while sodium butyrate treatment significantly increased the content of butyric acid and significantly decreased the content of propionic acid(P < 0.05).Sodium acetate and sodium butyrate treatment decreased the p H of duodenal and cecum contents(P < 0.05).Sodium acetate and sodium butyrate increased the diversity of the microbial community,with an increased abundance of Oscillospira,Bacteroides,and Akkermansia and decreased abundance of Ruminococcus in both treatment groups.The abundance of Rikenella in Acetate group decreased,while the abundance of Parabacteroids and Rikenella in Butyrate group increased.Pearson correlation analysis showed that Acetate group of Oscillospira and Bacteroides were significantly negatively correlated with IL-1β and Ig G(P < 0.05).The abundance of Oscillospira and Bacteroides in Butyrate group was significantly negatively correlated with IL-1β,TNF-α,Ig G,and Ig M,and significantly positively correlated with IL-17 and s Ig A(P <0.05).Ruminococcus were significantly and positively correlated with IL-1β in both treatment groups(P < 0.05).WGCNA results showed that the Meyellow module in Acetate group was significantly positively correlated with s Ig A,the MEmidnightblue module was significantly negatively correlated with IL-1β,and MEblack module was significantly positively correlated with IL-22(P < 0.05).The MEgreenyellow module and MEmagenta module of Butyrate group were significantly negatively correlated with Ig M(P < 0.05).Oscillospira and Lachnospiraceae are central to the immune factors IL-1β,IL-22,and s Ig A and could be potential immune-related probiotics in rabbits.(4)Effects of dietary supplementation of sodium acetate and sodium butyrate to diets on RNA-seq of cecum tissues in New Zealand white rabbits.Based on RNA-seq analysis of cecum tissues,a total of 648 functional genes were identified as DEGs in the acetate group,of which 368 were up-regulated and 280 were down-regulated,and a total of 466 functional genes were identified as DEGs in the butyric acid group,of which 250 were up-regulated and 216 were down-regulated,compared with the control group.According to GO and KEGG analysis,the upregulated DEGs were mainly enriched in cell cycle,cell proliferation,DNA replication,and ABC transporter protein signaling pathways.In addition,the up-regulated DEGs in Acetate group was also enriched in chemokine signaling pathway,and the up-regulated DEGs in Butyrate group was enriched in fructose and mannose metabolism,biosynthesis of unsaturated fatty acids,and folate biosynthesis.(5)Effects of sodium acetate and sodium butyrate on the proliferation and migration of CECs in New Zealand white rabbits.In this study,we successfully isolated CECs from New Zealand white rabbits and constructed a model of cecum epithelial cell proliferation and cecum epithelial cell injury by sodium acetate and sodium butyrate.It was further shown that sodium acetate and sodium butyrate stimulated the proliferation and migration of CECs in vivo and in vitro by activating the Wnt/β-catenin signaling pathway,and the expression of genes related to cell proliferation(PCNA,MKI67,TK1,CCNB2)was significantly increased(P < 0.05).In conclusion,the supplementation of sodium acetate and sodium butyrate to the diet could improve the productive performance and meat quality of rabbits by regulating cecum microecology and cecum epithelial cells.Sodium acetate and sodium butyrate played key roles in decreasing FCR and diarrhoea index,increasing total muscle fiber and muscle fiber density,preserving cecum villous tissue integrity and increasing cecum resistance to oxidative stress and immunity,as well as increasing cecum microbiome diversity and probiotic flora abundance in rabbits.In addition,both in vivo and in vitro assays demonstrated that sodium acetate and sodium butyrate may promote the proliferation and migration of CECs by activating the Wnt/β-catenin signaling pathway.This study provides important insights into how sodium acetate and sodium butyrate affect growth performance and cecal microecology in New Zealand white rabbits,demonstrating that dietary supplementation with sodium acetate and sodium butyrate may be an effective strategy to improve the productive performance of rabbits. |
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